ALGORITHM FOR DETECTING A SEIZURE FROM CARDIAC DATA
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Accused Products
Abstract
Methods, systems, and apparatus for detecting the seizure in a patient using a medical device. The determination is performed by collecting cardiac data determining valid heart beats suitable for seizure detection from the cardiac data; calculating heart rate data of interest from the valid heart beats; and identifying a seizure event from the heart rate data. The medical device may then take a responsive action, such as warning, logging the time of the seizure, computing and storing one or more seizure severity indices, and/or treating the seizure.
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Citations
43 Claims
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1-24. -24. (canceled)
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25. A method for detecting epileptic seizures based upon a time of beat sequence of the patient'"'"'s heart comprising:
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obtaining a time series of fiducial time markers for candidate heartbeats; identifying valid beats from said candidate heartbeats by subjecting a plurality of candidate beats to at least one beat validity test, said at least one beat validity test comprising at least one beat interval test applied to a candidate beat interval derived from a candidate heartbeat and at least one preceding heartbeat; accepting as valid beats the candidate beats that pass said at least one beat validity test; forming a first window from a first valid beat and at least one prior valid beat, wherein said first window is selected from; a time window of from 1 to 10 seconds, bounded on the most recent end by said first valid beat; and a number of beats window comprising said first valid beat and a number of immediately preceding beats ranging from 2-15; testing said first window with at least one window test, wherein said at least one window test comprises a dispersion test; accepting the beats in said window as suitable for seizure detection if said window has a dispersion less than a threshold level of dispersion; in response to accepting the beats in said window as suitable for seizure detection, determining a foreground heart rate parameter comprising a statistical measure of central tendency of heart rate in said first window; forming a second window larger than said first window; determining a background heart rate parameter comprising a statistical measure of central tendency of heart rate in said second window; determining a relative heart rate comprising at least one of a first ratio of said foreground and said background heart rate parameters and a second ratio of said background and said foreground heart rate parameters; comparing said relative heart rate to at least one of a first seizure threshold value associated with said first ratio and a second seizure threshold value associated with said second ratio; and detecting an epileptic seizure if at least one of said first ratio exceeds said first seizure threshold value, or said second ratio is below said second seizure threshold value. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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41. A method for detecting epileptic seizures based upon a time of beat sequence of the patient'"'"'s heart comprising:
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obtaining a time series of fiducial time markers for candidate heartbeats; identifying valid beats from said candidate heartbeats by subjecting a plurality of candidate beats to at least one beat validity test, said at least one beat validity test comprising at least one beat interval test applied to a candidate beat interval derived from a candidate heartbeat and at least one preceding heartbeat; accepting as valid beats the candidate beats that pass said at least one beat validity test; forming a first window from a first valid beat and at least one prior valid beat, wherein said first window is selected from; a time window of from 1 to 10 seconds, bounded on the most recent end by said first valid beat; and a number of beats window comprising said first valid beat and a number of immediately preceding beats ranging from 2-15; testing said first window with at least one window test, wherein said at least one window test comprises determining whether the mean square error of a least squares linear fit of the beats in said first window is less than a threshold; determining a foreground heart rate parameter comprising a statistical measure of central tendency of heart rate in said first window, in response to determining that the mean square error of a least squares linear fit of the beats in said first window is less than a threshold, forming a second window larger than said first window; determining a background heart rate parameter comprising a statistical measure of central tendency of heart rate in said second window; determining a relative heart rate comprising at least one of a first ratio of said foreground and said background heart rate parameters and a second ratio of said background and said foreground heart rate parameters; comparing said relative heart rate to at least one of a first seizure threshold value associated with said first ratio and a second seizure threshold value associated with said second ratio; and detecting an epileptic seizure if at least one of said first ratio exceeds said first seizure threshold value, or said second ratio is below said second seizure threshold value.
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42. A method for detecting epileptic seizures based upon a time of beat sequence of the patient'"'"'s heart comprising:
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obtaining by a cardiac data collection module a time of beat sequence for a series of candidate heartbeats; identifying by a heartbeat determination module a series of candidate beat intervals from pairs of adjacent candidate heartbeats; testing by a heartbeat validation module at least a plurality of candidate heartbeats with at least one beat validity test selected from; a) determining that a beat interval determined from said candidate heartbeat and the immediately preceding valid heartbeat is less than a maximum beat interval and greater than a minimum beat interval; b) determining that a beat interval determined from said candidate heartbeat and the immediately preceding valid heartbeat is within an acceptable percentage of at least one of the immediately preceding beat interval or a recent short term beat interval measure; and c) determining that the slope of a beat interval determined from said candidate beat and the immediately preceding valid heartbeat does not correspond to a rate of change of heart rate that is physiologically improbable; accepting by said heartbeat validation module as valid beats each candidate heartbeat passing said at least one beat interval test; identifying by a window test module a plurality of beats suitable for seizure detection by forming a first window comprising a first valid beat and at least one preceding heartbeat, wherein said first window is selected from a time window of from 1 to 10 seconds, bounded on the most recent end by said first valid beat; and a number of beats window comprising said first valid beat and a number of immediately preceding beats ranging from 2-15; testing with said window test module said beats in said first window with at least one window test, wherein said at least one window test comprises determining whether the mean square error of a least squares linear fit of the beats in said first window is less than a dispersion threshold; determining by a foreground/background module, in response to determining that the mean square error of a least squares linear fit of the beats in said first window is less than said dispersion threshold, a foreground heart rate parameter comprising a statistical measure of central tendency in said first window; forming by said foreground/background module a background window larger than said first window; determining by said foreground/background a background heart rate parameter comprising a statistical measure of central tendency in said background window; determining by a seizure detection module a relative heart rate parameter comprising at least one of the ratio of said foreground and said background heart rate parameters and the ratio of said background and said foreground heart rate parameters; comparing by said seizure detection module said relative heart rate parameter to a seizure threshold value; and detecting by said seizure detection module the occurrence of a seizure event if said relative heart rate parameter exceeds said seizure threshold value. - View Dependent Claims (43)
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Specification